Abstract: Porosity is critical to reservoir prediction, reservoir description, reservoir estimation and comprehensive reservoir study. It's also a critical technology to accurate estimation of oil reserve. Because of the strong heterogeneity of carbonate rock and strong lateral variation, the porosity prediction has remained a difficult problem for carbonate reservoir. Moreover, the accuracy of conventional method to calculate the porosity is not high enough and the physical meaning is always not so clear, it is hard to meet the needs of exploration and development. Therefore, through the reasonable simplification of the Gassmann equation and the introduction of Eshelby-Walsh dry rock ellipsoidal inclusions approximate formula, we derived a new formula to calculate the porosity. Three parameters, i.e. the pore structure parameters, saturated rock compressibility and rock matrix compressibility are included. Then through the intersection of logging technique charts and the inversion of pre-stack elastic parameters into the pore structure of carbonate and P-wave and S-wave velocity and density in the specific formula, considering the influence of carbonate rock pore structure with different phase, and the new method was applied. The results show that the porosity prediction method of carbonate rock pore structure has higher accuracy than the conventional method based on.